In some cases, a 3GPP LTE (3rd Generation Partnership Project Radio Access Network Long Term Evolution) system includes a femto (Femto) base station (hereinafter, may be referred to as a “femto station”). The femto station is smaller in size than a macro base station and installed in, for example, home or office.
At present, the femto base station differs for each communication carrier. Therefore, in an area where a plurality of users having communication terminals using different communication carriers come and go (for example, an office or a restaurant), femto stations corresponding to respective communication carriers are installed in order to cope with communication terminals of all the communication carriers. Consequently, burden on a person who installs the femto stations increases.    Patent Document 1: Japanese National Publication of International Patent Application No. 2012-502521
Meanwhile, it may be possible to introduce a femto station that can be shared by a plurality of communication terminals using different communication carriers. In this case, one of the communication carriers is assigned to each “cell” of the femto station. The “cell” is a unit of a frequency band that a single terminal performing communication can occupy.
However, if cells are simply assigned to a plurality of communication carriers, for example, excess cells may be assigned to a communication carrier that has a small number of communication terminals. In this case, the use efficiency of the cell is reduced.